Δ* - deltaStar Online v1.0 User's Guide
Δ* - deltaStar Online v1.0 User's Guide

  Introduction
  GPL
Application

HowTo Search Double Stars
  Overview
Refining Results
    By Coordinates
    By WDS Identifier
    By Minimum Separation
    By Minumum Primary Magnitude
Interpreting Results

Glossary

Source Code Download

 

Introduction

 

GPL

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deltaStar - Searches double star records in WDS data file. Copyright © 2012- Frederick (Rick) Burton @ DataPathways.com

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

Application

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deltaStar performs a selection of searches for double stars based on U.S. Naval Observatory Washington Double Star Catalog (WDS) records. NOTE: The data file is available here http://ad.usno.navy.mil/wds/Webtextfiles/wdsweb_summ.txt


 

HowTo Search Double Stars

 

Overview

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Position Criteria

  • Select criteria values from the droplists in the upper left portion of the deltaStar screen, then click the "Search" button.
  • Right Ascension criteria specify a North/South "slice" of the sky to search.
  • Delclination criteria specify an East/West "belt" of the sky to search.
  • TIP: The default values 00 and North respectively search a 15 degree "slice" of sky beginning at the celestial equator and reaching a point at the celestial north pole (very near Polaris, the North Star).

WDS Identifier

  • Enter a specific 10-character identifier rather than position coordinates.
  • Position Controls discussed above are disabled when an identifier is in use. Other controls remain enabled at all times.
  • TIP: Search an area of the sky first by position. Select a specific identifier of any resulting line item. Copy/paste or enter this code manually. Narrow this result by separation and magnitude. (See section below).

Separation and Magnitude Criteria

  • Separation and Magnitude criteria set limits on visual distance between stars and brightness of the primary, or brighter, star.
  • When a "Minumum Sep Arc Secs" value is selected, only stars with that amount of visual separation, in arc seconds, or more will be displayed. (See Glossary).
  • When a "Minumum Primary Magnitude" value is selected, only systems having a primary star of that magnitude or brighter will be displayed. (See Glossary).
  • TIP: When neither "Minumum Sep Arc Secs" value nor "Minumum Primary Magnitude" value is selected, all double stars in the designated area of the sky are displayed.

Refining Search Results

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Right Ascension

A Right Ascension Hour is selected with values ranging from 00 to 23, then 10s of Minutes and 1s of (single) Minutes may be selected within the chosen Hour. These values narrow the "slice" of sky to search progressively.

Declination

Declination may first be selected as North or South of the celestial equator. Next 10s of Degrees and 1s of (single) Degrees may be selected to further narrow the "belt" of the sky to search.

TIP: The Right Ascension "slice" and Declination "belt" intersect specifying a larger or smaller area of the sky to search. This can be very useful in identifying and verifying observations.

WDS Identifier

The first 10 characters of any record, the WDS Identifier, specify a particular double (multiple) star system. One or more records may contain this identifier, but each of these records describes the same star system. This code is established by Washington Double Star staff.

TIP: Once an area of the sky is searched by coordinates, it is often helpful to select one star system from the resulting list for observation planning or verification. This search may also be narrowed by separation and/or magnitude criteria to target various equipment used in observation. Note that a partial Identifier may be used!

Minimum Separation Arc Secs

Minimum Separation values limit how close the stars can be visually. This can also be helpful depending on available equipment for observing (eyes, binoculars, small telescope, large telescope).

TIP: Exaggerated differences in magnitude can further limit the ability to see very closely separated stars.

Minimum Primary Magnitude

Minumum Primary Magnitude values limit how dim the brightest star may be. This is also helpful in allowing for available observing equipment (eyes, binoculars, small telescope, large telescope).

TIP: Separation and Magnitude values are very useful in planning observations. They may also aid in further refining searches for identifying and verifying observations.


Interpreting Search Results

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Resources found on the U.S. Naval Observatory's Washington Double Star Catalog server.

Format TIP: Especially read the section "Columns 108-111" for code letters.
Notes
References and discoverer codes


 

Glossary

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  Right Ascension: Astronomical Longitude. Each hour equals 15 degrees and is divided into minutes and seconds of arc.

Declination: Astronomical Latitude. Degrees mirror terrestrial latitude with negative numbers representing southern locations.

Magnitude: Brightness Scale. Each whole number represents a change in brightness by a factor of 2.512 (5th root of 100) so that every five whole numbers represents a change in brightness by a factor of 100. Smaller values indicate greater brightness. A magnitude of 6.0 is naked-eye threshold.

Arc Seconds: A measure of visual distance between objects. One degree is 1/360th of a circle around the sky at the largest point (such as the celectial equator). An arc minute is 1/60th of a degree while an arc second is 1/60th of an arc minute. There are 1,296,000 arc seconds spanning the entire horizon!

EPOCH: First and last years of observation. THETA and RHO refer to these dates.

THETA: The Position Angle (PA) of a double star. Determined by the direction, as degrees on a compass, with the celestial North Pole at north.

RHO: The visual separation of a double star in arc seconds.

Spectral Type: A star's color or temperature on a blue to red scale using the designation letters O B A F G K M. O is blue/hottest while M is red/coolest.

Proper Motion: A star's movement in the sky against the "stationary" backdrop of more distant objects measured in arc seconds of Right Ascension and Declination per year.